I don't think that I've modified the data you're referring to in Pic_5 and Pic_6 with v2.78. It's data that is outside of the Apple iTunes metadata.
My guess is that you've used it on files that didn't have this special DRM part that files of kind "Purchased AAC audio file" have.
The drms atom of those files contains a little bit more than the user's name (it's what you've found next to the name atom). It contains user which most likely is the iTunes Store user ID, key which is most likely the iTunes Store user key and some more atoms which can possibly contain user-related information.